package com.lagou.sqlSession;

import com.lagou.config.BoundSql;
import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import com.lagou.utils.GenericTokenParser;
import com.lagou.utils.ParameterMapping;
import com.lagou.utils.ParameterMappingTokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.math.BigDecimal;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.util.ArrayList;
import java.util.List;

public class SimpleExecutor implements Executor {

    @Override
    public int update(Configuration configuration, MappedStatement mappedStatement, Object... param) throws Exception {

        // 1、注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();
        connection.setAutoCommit(true);

        // 2、获取sql语句：select * from user where id = #{id} and username = #{username}
        //转换sql语句: select * from user where id = ? and username = ?，转换过程中还需对#{}里的值进行解析存储
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        // 3、获取预处理对象：preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        // 4、设置参数
        //获取到了参数类的全路径
        String parameterType = mappedStatement.getParameterType();
        Class<?> parameterTypeClass = getClassType(parameterType);

        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String fieldName = parameterMapping.getFieldName();

            //反射
            Field declaredField = parameterTypeClass.getDeclaredField(fieldName);
            //暴力访问
            declaredField.setAccessible(true);
            Object obj = declaredField.get(param[0]);

            preparedStatement.setObject(i + 1, obj);

        }

        // 5、执行sql
        int count = preparedStatement.executeUpdate();

        return count;
    }

    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... param) throws Exception {

        // 1、注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();

        // 2、获取sql语句：select * from user where id = #{id} and username = #{username}
        //转换sql语句: select * from user where id = ? and username = ?，转换过程中还需对#{}里的值进行解析存储
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        // 3、获取预处理对象：preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        // 4、设置参数
        //获取到了参数类的全路径
        String parameterType = mappedStatement.getParameterType();
        Class<?> parameterTypeClass = getClassType(parameterType);

        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String fieldName = parameterMapping.getFieldName();

            //反射
            Field declaredField = parameterTypeClass.getDeclaredField(fieldName);
            //暴力访问
            declaredField.setAccessible(true);
            Object obj = declaredField.get(param[0]);

            preparedStatement.setObject(i + 1, obj);

        }

        // 5、执行sql
        ResultSet resultSet = preparedStatement.executeQuery();
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);

        ArrayList<Object> objects = new ArrayList<Object>();

        // 6、封装返回结果集
        while (resultSet.next()) {
            Object o = resultTypeClass.getDeclaredConstructor().newInstance();
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <= metaData.getColumnCount(); i++) {
                //字段名
                String columnName = metaData.getColumnName(i);
                //字段值
                Object columnValue = resultSet.getObject(columnName);

                //使用反射或者内省，根据数据库表和实体对应关系，完后封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);//构造时会为类的属性生成读写方法
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o, columnValue); //调用写方法，完成列值到属性的赋值
            }
            objects.add(o);
        }

        return (List<E>) objects;
    }

    private Class<?> getClassType(String parameterType) throws ClassNotFoundException {
        if (parameterType != null) {
            Class<?> aClass = Class.forName(parameterType);
            return aClass;
        }

        return null;
    }

    /**
     * 完成对#{}的解析：1、将#{}替换为? 2、解析出#{}里的值进行存储
     *
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql) {
        //标记处理类：配置标记解析器来完成对占位符的解析处理工作
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
        //解析出来的sql
        String parseSql = genericTokenParser.parse(sql);
        //解析出来的#{}里的参数名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();
        BoundSql boundSql = new BoundSql(parseSql, parameterMappings);

        return boundSql;
    }
}
